Safety burner control apparatus



Oct. 11, 1955 Q 13, WARD 2,720,254

SAFETY BURNER CONTROL APPARATUS Filed April 2, 1952 ON HEATING 5l-OPE-s,s2-cl.osEs. so-o eus ON COOLING 52-OPENS, 50-6LOSES, SI-GLOSES IN VEN TOR. CARL D. WARD Mx M ATTORNEY United States Patent SAFETY BURNERcor-srnor APPARATUS Carl D. Ward, Minneapolis, Minn, assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application April 2, 1952, Serial No. 280,103

11 Claims. (Cl. 15828) This invention relates to a burner controlapparatus having a safety cutout device, an ignition timer, and a safetyinterlock circuit such that the burner control apparatus offers amaximum protection against unsafe conditions which may arise at theburner unit being controlled.

The prior art devices have incorporated one or more of the abovementioned features into burner controls, however, these burner controlsfor the most part have been complex circuits having a great number ofcomponents which from the cost standpoint rendered these prior artdevices unsuccessful in the competitive market.

It is therefore an object of the present invention to provide animproved burner control apparatus having a minimum number of componentsand incorporating a novel circuit whereby the ignition timer actuatorand the safety cutout actuator are electrically interconnected toprovide for energization for the safety cutout actuator until flame isestablished at the controlled fuel burner and then to provide fordeenergization of the safety cutout actuator and energization of theignition timer actuator.

It is the further object of the present invention to provide an improvedburner control apparatus wherein an ignition timer controls, in circuitclosing position, the supply of power to an ignition means of a burnerunit and also controls a safety interlock circuit to insure that powercannot be applied to the burner control apparatus until the ignitiontimer is in its circuit closing position.

It is a further object of the present invention to provide an improvedburner control apparatus wherein a burner control relay is operativelyenergized upon a need for operation of the burner control unit toinitiate a starting period for a fuel burner during which a safetycutout device is energized, and upon the establishment of combustionatthe fuel burner a holding circuit is established for the burnercontrol relay and a running period is initiated for the fuel burnerwherein a post ignition timer is energized to subsequently deenergize anignition transformer, with the initial energizing circuit of the burnercontrol itself being initially dependent upon the post ignition timerbeing in its circuit closing position and on the burner control relaybeing in its deenergized position and with a holding energizationcircuit formed for the burner control when the burner control relayassumes its energized position.

Figure 1 is a showing of the improved burner control apparatus, and;

Figure 2 is a showing of a modification of a portion of the burnercontrol apparatus of Figure 1.

Referring specifically to Figure l, a fuel burner unit is shown having afuel burner 11 and an ignition means 12. The burner unit 10 iscontrolled by the improved burner control apparatus shown within brokenlines 13, and the apparatus 13 is under the control of a thermostatshown within the broken lines 14, which thermostat is responsive to aneed for operation of the burner unit 10 to close contacts 15 and 16.

Referring specifically to the improved burner control apparatus 13, aburner control relay 17 is provided hav- 2,720,254 Patented Oct. 11,1955 ing a relay winding 18, and an armature 19. The armature 19 of therelay 17 is shown in its inoperative or deenergized position and isprovided with bridging bars 20 and 21. Upon energization of the relaywinding 18, the armature 19 moves the bridging bar 20 into engagementwith in contacts 22 and 23 and the bridging bar 21 into engagement within contacts 24 and 25. A relay out contact 26 is provided for the relay17. Contact blade 27 engages out contact 26 and is connected to andmovable with the in contact 25. Upon energization of the relay winding18 the armature 19 moves the bridging bars 20 and 21 into engagementwith the in contacts and due to the press back of the relay the incontacts 2255' are moved to the left to broken line position 28. Themovement of the in contacts to this broken line position 28 moves incontact 25 and contact blade 27 to the left and causes the blade 27 todisengage the out contact 26.

Also included within the burner control apparatus 13 is a safety cutoutdevice 30 having normally closed contacts 31 and 32, a bimetal member33, a reset actuator 34, and an electrically energizable actuatingheater 35. Upon a predetermined time period of energization of theheater 35, the bimetal 33 warps to the right out from under the normallyclosed contacts 31 and 32 to allow the contacts to disengage. Upon asubsequent cooling of the bimetal element 33, the reset actuator 34 canbe depressed to reset the contacts 31 and 32 to their normal position asshown in the figure.

A timer 36 is provided having an electrically energizable actuatingheater 39, and a normally closed cold switch comprising a contact 37,and a bimetal member 38. After a predetermined time period ofenergization of the heater 39 above a given minimum energization level,the bimetal element 38 warps to the left to disengage contact 37. Uponthe bimetal element 38 cooling the element 38 again engages contact 37as shown in the figure.

A combustion responsive means 40 is shown having a hot closed switch 52,a first cold closed switch 51, and a second cold closed switch 50. Abimetal actuator is shown at 46 and is normally located to be responsiveto the presence or absence of combustion at the burner unit 10. Thebimetal actuator 46 is effective upon heating to move to the left asshown by the arrow in Figure 1. Movement of bimetal actuator 46 istransmitted by means of a rod, shown by dotted line 47, and by members200 and 201 to the switches 50, 51 and 52.

The members 200 and 201 are mounted in slip friction engagement with therod, shown by dotted line 47, and move with the rod until sufiicientforce is applied to stop such movement, at which time the members 200and 201 will remain stationary and slide upon the rod.

The blades upon which switches 50 and 51 are mounted are biased so thatas member 200 moves to the left the switches 50 and 51 also move to theleft until stops 202 and 203 are engaged to cause switches 51 and 50respectively to open. The blade upon which the right hand member ofswitch 52 is mounted is biased to the right to engage member 201.

The combustion responsive means 40 is shown in the cold position inFigure 1, that is, with no flame present at the burner unit 10. Uponcombustion being established at the burner unit 10, the bimetal actuator46 begins to move to the left. This movement causes members 200 and 201to also move to the left. When member 200 has moved a predetermineddistance, the right hand member of cold closed switch 51 engages stop202 to stop this member. Further movement of member 200 causes coldclosed switch 51 to open.

During this movement of member 200, member 201 has also moved to theleft and a short time of movement after cold closed switch 51 opens, hotclosed switch 52 closes. Again after a short time of movement, stop 203engages the common member of cold closed switches 50 and 51 and furthermovement of member 200 to the left causes cold closed switch 50 to open.

When combustion ceases at the burner unit 10, the bimetal actuator 46cools and moves to the right to the position shown in Figure 1. Firstinitial movement to the right causes member 201 to also move to theright and open thereby hot closed switch 52. Further movement to theright causes member 200 to close cold closed switch 50. Still furthermovement to the right causes cold closed switch 51 to be closed.

A transformer 53 having a primary 54 and a secondary 55 is shownassociated within the burner control apparatus 13 to supply power tocircuits which include the burner control relay 17, the timer 36, thesafety cutout device 30, and the hot closed and cold closed switches ofthe combustion responsive means 40. A plurality of terminals are alsoassociated with the burner control apparatus 13. The terminals 56 and 57are the power input terminals to the burner control apparatus 13 and areadapted to be connected to a source of electrical power, which power issupplied to the burner unit under the control of the burner controlapparatus 13 and the thermostat 14. The terminals 58 and 59 are adaptedto be connected to the thermostat 14 and are efiectively connectedtogether upon a need for operation of the burner unit 10 which thethermostat 14 senses by closing the contacts and 16. Terminal 60 isadapted to be connected to the ignition means 12 of the burner unit 10while terminal 61 is adapted to be connected to the burner 11 of theburner unit 10.

Operation Referring to the Figure 1, the apparatus is shown in itsstandby condition. That is, the timer 36 has its normally closed coldswitch in the closed position, the safety cutout device has its contacts31 and 32 in engaging position, the relay 17 is in its deenergizedposition, and the combustion responsive means 40 is in a conditionindicating the absence of combustion at the burner unit 10.

Assuming that power is applied to the power input terminals 56 and 57,an initial energizing circuit can be traced for the primary 54 of thetransformer 53 from the power input terminal 56 through the primary 54,conductor 62, bimetal element 38 and contact 37 of the timer 36,conductor63, contact blade 27 and out contact 26 of the relay 17,conductor 64, and conductor 65 to the power input terminal 57. From thislast traced circuit it can be seen that in the standby condition inorder for power to be applied to the primary 54 it is necessary first,for the closed cold switch of timer 36 to be in its cold position, andsecond, for the relay armature 19 to be in its deener gized positionsuch that the switch blade 27 engages the out contact 26. This importantfeature will be discussed more fully later.

Assume now that there is a need for operation of the burner unit 10which the thermostat 14 senses by closing the contacts 15 and 16. Aninitial energizing circuit can now be traced for the relay 17 from theupper terminal of the secondary 55 through conductor 66, contacts 32 and31 of the safety cutout device 30, relay winding 18, terminal 59,thermostat 14, terminal 58, conductor 67, conductor 68, heater of thesafety cutout device 30, conductor 69, cold closed switch 51, conductor70, and conductor 71 to the lower terminal of the secondary 55., At thispoint it should be noted that a shunt circuit can be traced around theheater 35 of the safety cutout device 30 from conductor 67 throughconductor 100, resistor 73, conductor 74, and cold closed switch 50 ofthe combustion responsive means to conductor 70, which circuit thereforeplaces the heater 35 in parallel with resistor 73. This last tracedcircuit is a first nonpickup holding circuit for relay 17. This isappropriately called a non-pickup holding circuit since the impedance ofthe resistor 73 is such that the level of energization furnished by thiscircuit to relay winding 18 of the relay 17 is below that valuenecessary for the relay armature 19 to move from its inoperative to itsoperative position but of a sufficient level to maintain the armature 19at its operative position. in other words, if it is assumed for the sakeof explanation that the relay 17 is energized initially through thisnon-pickup holding circuit, the relay armature 19 will not be moved intoengagement with the in contacts of the relay 17 since the level ofenergization furnished to winding 18 is insufiicient to cause thearmature 19 to be moved.

In this phase of operation of the burner control apparatus 13 theactuator 35 of the safety cutout device 30 is operatively energized,that is, if the combustion responsive means 40 does not operate toindicate the establishment of combustion the safety cutout device 30will be actuated to the position where the contacts 31 and 32 aredisengaged. By way of illustration, it has been found desirable toselect the following impedance values for the actuating heaters 35 and39 and the resistor 73:

Ohms Actuating heater 35 8 Actuating heater 39 28 Resistor 73 30 Fromthe above values, it can be seen that the above traced shunt circuit hasan impedance value of 30 ohms while the impedance of safety cutoutheater 35 is only 8 ohms and therefore for all practical purposes theshunt circuit has a negligible amount of the electric current flowingthrough it. It is intended that the above stated impedance values in noway limit the present invention but these impedance values are given tomore clearly point out the manner in which the actuator 35 isoperatively energized in this initial phase of operation of burnercontrol apparatus 13.

Energization of the relay 17 causes the relay armature 19 to move thebridging bars 20 and 21 into engagement with the in contacts 22 through25 of the relay 17 Consider at this time the instant when the bridgingbars 20 and 21 have just engaged the in contacts 22 through 25 of therelay 17. The initial energizing circuit for the primary 54, abovetraced, is still completed through contact blade 27 and out contact 26of the relay 17, however, aholding circuit is now also established forthe primary 54. This holding circuit can be traced from the power inputterminal 56 through primary 54, conductor 62, conductor 80, bridging bar20, in contact 22 of relay 17, conductor 81, and conductor to the powerinput terminal 57. The relay armature 19 now completes its movement totake up the press back of the relay and moves the in contacts 22 through25 to the left to the position shown by the broken line 28 and thereforecauses contact blade 27 to disengage out contact 26 of the relay 17.This breaks the initial energizing circuit for primary 54 of thetransformer 53, however, the above traced holding circuit is effectiveto supply power to the primary 54 so long as the relay 17 remains in itsenergized position.

The movement of the relay armature 19 to its energized position causespower to be supplied to the burner unit 10 through the terminals 60 and61. The energizing circuit for the burner motor 11 can be traced frompower line 82 through conductor 83, conductor 84, burner motor 11,conductor 35, terminal 61, conductor 86, in contact 23, bridging bar 20and in contact 22 of the relay 17, conductor 81, conductor 65, and powerinput terminal 57 to power line conductor 87. The energizing circuit forthe ignition means 12 can be traced from the power line conductor 82through conductor 83, ignition means 12, conductor 88, terminal 68,conductor 89, in contact 24, bridging bar 21 and in contact 25 of relay17, conductor 63, contact 37 and bimetal 38 of the timer 36, conductor80, bridging bar 20 and in contact 22 of relay 17, conductor 81,conductor 65, and power input terminal 57 to power line conductor 87.

This is the starting phase of the burner control unit 13 wherein theburner motor 11 is energized, the ignition means 12 is energized, thetimer 36 is operatively deenergized, and the safety cutout device 30 isoperatively energized.

Assume now that a flame is established at the burner unit 10, thebimetal actuator 46 of the combustion responsive means 40 will respondto the presence of combustion at the burner unit and will actuate itsassociated hot closed and cold closed switch in the sequence abovedescribed. The bimetal actuator 46 will first cause the cold closedswitch 51 to open. The opening of the cold closed switch 51 opens theinitial energizing circuit for the relay 17 and renders the above tracedfirst nonpickup holding circuit effective to maintain the relayenergized. The opening of the cold closed switch 51 thereforedeenergizes the heater 35 of the safety cutout device 30. The timingperiod of the safety cutout device is so selected that for a normalstart up of the burner unit 10 a flame is established and bimetalactuator 46 of the combustion responsive means 40 responds to theestablishment of combustion to deenergize the heater of the safetycutout device 30 before the safety cutout contacts 31 and 32 disengage.

A short time after the opening of the cold closed switch 51, the hotclosed switch 52 of the combustion responsive means closes. The closingof the hot closed switch 52 initiates the establishment of a secondnon-pickup holding circuit for the relay 17. This second non-pickupholding circuit can be traced from the upper terminal of secondary 55 ofthe transformer 53 through conductor 66, contacts 32 and 31 of thesafety cutout device 30, relay winding 18, terminal 59, thermostat 14,terminal 58, conductor 67, conductor 72, heater 39 of the timer 36,conductor 101, hot closed switch 52 of the combustion responsive means40, conductor 91, and conductor 71 to the lower terminal of thesecondary 55.

At this time both the above mentioned first non-pickup holding circuitand the second non-pickup holding circuit are energized. It will benoted that the resistor 73 is now in parallel with heater 39 of thetimer 36. However the heater 39 remains operatively deenergized, thatis, the level of energization supplied to the heater 39 at this time isnot sufficient to cause the bimetal 38 to disengage contact 37 of thetimer 36. This can readily be seen by referring to the above table ofimpedance values given for purposes of illustration. From this table itcan be seen that the 28 ohm actuating heater 39 of the timer 36 has inparallel therewith the 30 ohm resistor 73 and for this condition theheater 39 remains operatively deenergized.

A short period of time after the closing of the hot closed switch 52,the cold closed switch of the combustion responsive means 40 opens toopen the above mentioned first non-pickup holding circuit. The functionof the cold closed switch 50 will be explained in greater detail later.

With the opening of the above traced first non-pickup holding circuitfor the relay 17 heater 39 of the timer 36 is operatively energizedsince the heater 39 is no longer in parallel with resistor 73 and theentire relay current flows through the heater 39 to operatively energizethe heater 39.

A predetermined time after the establishment of this second non-pickupholding circuit, the bimetal 38 of the timer 36 is heated to a conditionwhere the engagement of the bimetal 38 to the contact 37 is broken. Itwill be remembered that the energizing circuit for the ignition means 12dependent upon the cold closed switch of timer 36 being closed and uponthe relay armature 19 being in its energized position. Therefore, theopening of the cold closed switch of the timer 36 deenergizes theignition means 12 of the burner unit 10.

The burner control apparatus 13 is now in its running condition with theburner motor 11 energized, the ignition means 12 deenergized, the heater35 of the safety cutout.

device 30 deenergized, the bimetal actuator 46 of the combustionresponsive means 40 responding to the presence of combustion at theburner unit 10, and the heater 39 of the timer 36 operatively energizedto maintain the timer cold closed switch open.

Assume now that the thermostat 14 has been satisfied by a sufiicientperiod of operation of burner unit 10 and has accordingly opened thecontacts 15 and 16. The energizing circuit for the relay 17 is thereforebroken and the relay armature 19 returns to its inoperative positionsuch as shown in the Figure 1. This immediately deenergizes the burnerunit 11 and also breaks the holding circuit for primary 54 of thetransformer 53. As shown in the Figure l, the deenergization of relay 17causes switch blade 27 to engage out contact 26 of the relay 17.

The bimetal actuator 46 of the combustion responsive means 40 nowresponds with an inherent time delay to the absence of combustion at theburner unit 10 to operate its associated hot closed and cold closedswitches in the above mentioned sequence. The hot closed switch 52 firstopens. At this time the cold closed switches 50 and 51 and the hotclosed switch 52 are open. If at this time there is a second call forheat, as evidenced by the thermostat 14 closing the contacts 15 and 16,the relay 17 cannot be energized since the initial energizing circuitfor the relay and the non-pickup holding circuits for the relay are openat the associated hot closed and cold closed switches of the combustionresponsive means 40. Likewise, before another cycle of operation of theburner unit 10 can be initiated it is necessary for the bimetal 38 ofthe timer 36 to return to the cold position to close the normally closedcold switch and thereby close the initial energizing circuit of theprimary 54.

A short time after the opening of hot closed switch 52, cold closedswitch 50 of the combustion responsive means 40 closes. Assume for themoment that the cold closed switch of the timer 36 is now in the closedposition, to close the initial energizing circuit of primary 54, andthat there is a call for heat. The first non-pickup holding circuit forthe relay 17 can now be traced from the upper terminal of the secondary56 of the transformer 53 through conductor 66, contacts 32 and 31 of thesafety cutout device 30, winding 18, terminal 59, thermostat 14,terminal 58, conductor 67, conductor 100,

resistor 73, conductor 74, cold closed switch 50 of the combustionresponsive means 40, conductor 70, and con-' ductor 71 to the lowerterminal of the secondary 55. The resistor 73 limits the level ofenergization of the relay winding 18 below that which is necessary tocause the relay armature 19 to be moved to operative position so that atthis time the relay is not energized. A short time after the closing ofcold closed switch 50. the cold closed switch 51 closes.

It has been found that the combustion responsive means 40 at this pointin the operation of the apparatus 13 tends to produce an intermittentcondition of closing and opening of cold closed switch 51 for a shortperiod of time. It will be remembered that the initial energizingcircuit for the relay 17 includes the cold closed switch 51 and if itwere not for the cold closed switch 50 which is closed at this point toclose the first non-pickup holding circuit it would be possible for therelay armature 19 to move between its operative and inoperativepositions a number of times before the combustion responsive means 46positively closed cold closed switch 51.

To explain more fully the utility ofproviding the cold closed switch 50,consider that the cold closed switch 51 has been closed for a very shortperiod of time and then opened due to the inherent characteristics ofbimetal actuator 46 of the combustion responsive means 40. The initialclosing of the cold closed switch 51 completes the initial energizingcircuit for the relay 17 and the relay armature 19 moves from itsinoperative to its operative position. The cold closed switch 51 nowopens, however the relay is maintained energized through the firstnonpickup holding circuit, above traced, which includes in series withthe relay winding 18, the resistor 73, and the cold closed switch 50. Itis of course immediately recog nized that the cold closed switch 51 willagain immediately close and be positively closed by bimetal actuator 46of the combustion responsive means 40 to complete the initial energizingcircuit for the relay winding 18 which includes the heater 35 of thesafety cutout device 30.

Since it has been assumed that there is a call for heat as evidenced bythe closing of the contacts and 16 of the thermostat 14, the above cycleof operation will be repeated and a flame will again be established atthe burner unit 10.

Opemtion on flame failure Assume now that a flame is not established atthe burner unit 10 after control apparatus 13 has been energized upon acall for heat by the thermostat 14. The bimetal actuator 46 of thecombustion responsive means 40 will not therefore actuate the associatedhot closed and cold closed switches from the positions shown in theFigure 1 and the relay winding 18 will remain energized through theinitial energizing circuit which includes the heater 35 of the safetycutout device 30. After a predetermined time of energization of theheater 35 the safety cutout device will be actuated to cause thecontacts 31 and 32 to disengage. The relay 17 is therefore de'energizedarid the relay armature 19 assumes its inoperative position todeenergize the burner unit 10. However, the primary 54 of thetransformer 53 remains energized through the initial energizing circuitwhich includes the normally closed cold switch of the timer 36 and theout contact 26 of the relay 17. The opening of contacts 31 and 32 alsocauses the heater of the safety cutout device 30 to be deenergized andafter a predeter'mined length of time the bimetal 33 associated with thesafety cutout device 30 cools so that depressing the reset actuator 34resets the contacts 31 and 32 to their engaging position so that therelay 17 is again energized to make a second attempt to establish flameat the burner unit 10.

Assume now that the burner control apparatus 13, upon a call for heat bythe thermostat 14, has established the running condition at the burnerunit 10 and that there is a subsequent flame failure. The bimetalactuator 46 for the combustion responsive device will first open the hotclosed switch 52 to deenergize the relay 17 and thereby deenergize theburner motor 11. The cold closed switch will then close to energize theabove mentioned first non-pickup holding circuit for the relay 17. Ashort time thereafter the cold closed switch 51 will close and the relay17, the heater 35 of the safety cutout device 30 and the burner unit 10will again be energized to attempt to reestablish a flame at the burnerunit 10. If, due to some fault in the burner unit 10, a flame is notestablished the safety cutout device 30 will operate to break theenergizing circuit for the relay 17 at the safety cutout contacts 31 and32 and will also deenergize the heater 35 of the safety cutout device30. After a predetermined length of time bimetal 33 of the safety cutoutdevice 30 cools and the reset actuator 34 can be depressed to reset thecontacts 31 and 32 to their engaging position. If there is still a callfor heat by the thermostat 14 the burner unit 10 will again be energizedto attempt to establish flame at the burner unit.

Modification of Figure 2 Referring now specifically to Figure 2, amodification of the apparatus of Figure l is shown with the commonelements between the two figures retaining the same reference numerals.The modification of Figure 2 can be completely visualized by replacingthe circuitry of Figure 1, which includes the heaters 35 and 39, theresistor 73,

" tor 73.

and the hot closed and cold closed switches of the combustion responsivemeans 40, by the circuitry shown in Figure 2. In the modification ofFigure 2, the above described first non-pickup holding circuit for relay17 has been changed.

The initial energizing circuit for relay 17 in the apparatus of Figure lis identical with that in the modification of Figure 2 in that in bothinstances the circuit includes conductor 67 conductor 68, heater 35 ofsafety cutout device 30, conductor 69, cold closed switch 51 andconductor 70.

The first non-pickup holding circuit of Figure 2 diflfers from the firstnon-pickup holding circuit of Figure l in that this circuit of Figure 2includes the resistor 73 andheater 39. This first non-pickup holdingcircuit of Figure 2 can be traced from conductor 67 through conductor72, heater 39 of timer 36, resistor 73, conductor 74, and cold closedswitch 50 to conductor 7 0.

The second non-pickup holding circuit for relay 17 is substantiallyidentical in both Figures 1 and 2 in that in both instances the secondnon-pickup holding circuit includes the heater 39 of the timer 36 andthe hot closed switch 52 of the combustion responsive means 40.

Referring again to Figure 2, assume that thermostat 14 calls for heat byclosing contacts 15 and 16. The relay 17 will now be energized throughthe initial energizing circuit which includes conductor 67, conductor68, heater 35 of safety cutout device 30, conductor 69, cold closedswitch 51 of combustion responsive means 40, conductor 70, and conductor71. It will be noted that in parallel with the above traced initialenergizing circuit is the first non-pickup holding circuit which can betraced from conductor 67 through conductor 72, heater 39 of timer 36,resistor 73, conductor 74, cold closed switch 50 of combustionresponsive means 40, conductor 70, and conductor 71. At this time theheater 35 of the safety cutout device 30 is operatively energized whilethe heater 39 of the timer 36 is operatively deenergized. This can bemore clearly seen by referring to the table of impedance values forheaters 35 and 39 and resistor 73. The above traced initial energizingcircuit contains only the 8 ohm heater 35 for the safety cutout device30 while the first non-pickup holding circuit includes in series the 28ohm heater 39 for the timer 36 and the 30 ohm resis- It can therefore beseen that negligible current flows through the first non-pickup holdingcircuit at this time so that heater 39 is operatively deenergized.

A flame is now normally established at the burner unit 10 and thebimetal actuator 46 of the combustion responsive means 46 senses theflame and first opens the cold closed switch 51. This opens the initialenergizing circuit for relay 14 thereby deenergizing the heater 35 ofthe safety cutout device 30, however, the relay 17 remains energizedthrough the above traced first non-pickup holding circuit. At this timethe heater 35 of the safety cutout device 30 is operatively deenergizedand the heater 39 of the timer 36 remains operatively deenergized. It isrecognized that the level of energization of the heater 39 has increasedat this time due to the opening of the initial energizing circuit,however, the resistor 73 acts as a current limiting resistor andprevents the heater 39 from being operatively energized.

A short time after the opening of the cold closed switch 51 the hotclosed switch 52 closes. The closing of hot closed switch 52 completesthe second non-pickup holding circuit which can be traced from conductor67 through conductor 72, heater 39 of timer 36, conductor 90, hot closedswitch 52, and conductor 91 to conductor 71. It can be seen that thefunction of the hot closed switch 52 is to short out that portion of thefirst non-pickup holding circuit which includes resistor 73 therebyincreasing the level of energization in the heater 39 of the timer 36 toa point where the heater is now operatively energized.

A short time after closing of the hot closed switch 52 the cold closedswitch 50 opens to break the above mentioned first non-pickup holdingcircuit. After a predetermined time of energization of the heater 39,the timer 36 operates to disenage contact 37 from bimetal 38 to therebydeenergize the ignition means 12. The apparatus is now in its runningcondition.

Assume now that the thermostat 14 has been satisfied and that ittherefore opens contacts 15 and 16. The relay 17 will become deenergizedand therefore the burner unit will be deenergizedv The bimetallicactuator 46 of the combustion responsive means 40 senses the absence offlame at the burner unit 10 and first opens the hot closed switch 52. Ashort time thereafter the cold closed switch 50 closes to complete theabove mentioned first non-pickup holding circuit. It will be rememberedfrom the discussion above that if the thermostat 14 is again calling forheat at this time the relay 17 will not move armature 19 due to the factthat this first non-pickup holding circuit limits the level ofenergization of the relay 17 below that which is necessary to cause therelay 17 to move its armature 19 to the operative position.

A short time after the closing of cold closed switch 50 the cold closedswitch 51 closes. This completes the initial energizing circuit for therelay 17 and if at this time the thermostat 14 is calling for heat therelay 17 will be energized and the cycle of operation of the burnerapparatus 13 will be repeated to establish flame at the burner unit 10.

From the above description of the operation of the present invention itcan be seen that the burner control apparatus 13 maintains the heater 35of the safety cutout device 30 energized until the combustion responsivemeans 40 indicates that a flame is present at the burner unit 10 and inthe absence of the establishment of combustion at the burner unit 10 thesafety cutout device 30 deenergizes the relay 17 and thereby deenergizesthe burner unit 10 to prevent the unlimited supply of fuel in theabsence of combustion.

It can therefore be seen that I have provided an improved burner controlapparatus wherein an ignition timer functions with a single set ofcontacts to provide both ignition timing and interlocking means suchthat power cannot be applied to the burner control apparatus until theenergizing circuit for the ignition means is in a condition to becompleted upon energization of the burner control relay.

I claim as my invention:

1. A burner control apparatus for use with a fuel burner and a burnerignition means under the control of means responsive to the need foroperation of the burner, comprising; a relay arranged to be energizedupon a need for operation of the burner, first relay controlled swtchingmeans closed upon energization of said relay, second relay controlledswitching means opened upon energization of said relay, flame responsiveswitching means including means responsive to combustion at the fuelburner to actuate the switches of said flame responsive switching meansto a first condition upon the presence of combustion or to a secondcondition upon the absence of combustion at the fuel burner, timingmeans having timing switching means and an electrically operableactuator connected to be energized to open said timing switching meansafter a time delay upon the switches of said flame responsive switchingmeans assuming said first condition and to be operatively deenergized tothereby close said switching means after a time delay upon the switchesof said flame responsive switching means assuming said second condition,a transformer having a primary and a secondary winding, means connectingsaid secondary winding to energize said relay upon a need for operationof the burner and upon the switches of said flame responsive switchingmeans being in said second condition, energizing circuit meansconnecting said primary to terminals adapted to be connected to a sourceof power and depending upon said timing switching means being closed andsaid second relay controlled switching means being closed, circuit meansconnecting terminal means adapted to be connected through the fuelburner to a source of power and depending upon said first relaycontrolled switching means being closed, circuit means connectingterminal means adapted to be connected through the ignition means to asource of power depending upon said first relay controlled switchingmeans being closed and said timing switch means being closed, andholding circuit means for the primary of said transformer maintainingsaid primary energized after the opening of said timing switching meansand said second relay controlled switching means, said holding circuitmeans including said first relay controlled switching means in closedcondition.

2. Burner control apparatus for use with a fuel burner and burnerigniting means under the control of means responsive to the need foroperation of the fuel burner, comprising; a relay having a winding andswitching means which assume a first or a second condition dependingupon Whether said winding is deenergized or energized; a safety cutoutdevice having normally closed switch contacts and an electricallyenergizable actuator; a timer having a normally closed switch and anelectrically energizable actuator; combustion responsive means havingfirst and second sets of cold closed switches and a hot closed switch,said combustion responsive means arranged to open said first cold closedswitch, close said hot closed switch and then open said second coldclosed switch upon combustion being established; impedance means; aninitial energizing circuit for said relay arranged when completed tooperatively energize said relay winding and including terminals adaptedto be connected to means responsive to the need for operation of thefuel burner, the normally closed switch contacts and actuator of saidsafety cutout device, and said first cold closed switch of saidcombustion responsive means; a first holding circuit for said relay inparallel with the actuator of said safety cutout device including theactuator of said timer, said impedance means and said second cold closedswitch of said combustion responsive means, the relative impedance ofsaid initial energizing circuit and said first holding circuit beingsuch that the actuator of said safety cutout device is operativelyenergized and the actuator of said timer is operatively deenergized; asecond holding circuit for said relay in parallel with the actuator ofsaid safety cutout device including the actuator of said timer and saidhot closed switch of said combustion responsive means; said combustionresponsive means upon combustion being established opening said initialenergizing circuit for said relay to deenergize the actuator of saidcutout device and closing said second holding circuit for said relay toenergize the actuator of said timer; and circuit means arranged tosupply power to terminals adapted to be connected to a fuel burner andburner igniter, said last named circuit means depending upon said relayswitching means being in said second condition to supply power to thefuel burner and upon said timer switch being closed to supply power tothe burner igniter.

3. Burner control apparatus for use with a fuel burner and burnerigniting means under the control of means responsive to the need foroperation of the fuel burner, comprising; a relay having a winding andswitching means which assume a first or a second condition dependingupon whether said winding is operatively deenergized or energized; asafety cutout device having normally closed switch contacts and anelectrically energizable actuator; a timer having a normally closedswitch and an electrically energizable actuator; combustion responsivemeans having first and second cold closed switches and a hot closedswitch, said combustion responsive means arranged to open said firstcold closed switch, close said hot closed switch and then open saidsecond cold closed switch upon combustion being established; impedancemeans; an initial energizing circuit for said relay arranged whencompleted to operatively energize said relay winding and includingterminals adapted to be connected to means responsive to the need foroperation of the fuel burner, the normally closed switch contacts andactuator of said safety cutout device, and said first cold closed switchof said combustion responsive means; a first holding circuit for saidrelay in parallel with the actuator of said safety cutout deviceincluding the actuator of said timer, said impedance means and saidsecond cold closed switch of said combustion responsive means, therelative impedance of said initial energizing circuit and said firstholding circuit being such that the actuator of said safety cutoutdevice is operatively energized and the actuator of said timer isoperatively deenergized; a second holding circuit for said relay inparallel with the actuator of said safety cutout device including theactuator of said timer and said hot closed switch of said combustionresponsive means; said combustion responsive means upon combustion beingestablished opening said initial energizing cir cuit for said relay todeenergize the actuator of said cutout device and closing said secondholding circuit for said relay to energize the actuator of said timer;circuit means arranged to supply power to terminals adapted to beconnected to a fuel burner and burner igniter, said last named circuitmeans depending upon said relay switching means being in said secondcondition to supply power to the fuel burner and upon said timer switchbeing closed to supply power to the burner igniter; power inputterminals arranged to be connected to a source of power for supplyingpower to the above mentioned circuits; an initial power energizingcircuit for the above mentioned circuits including said power inputterminals, said relay switching means in said first position, and saidtimer switch in closed condition; and a power holding circuit for theabove mentioned circuits including said power input terminals and saidrelay switching means in said second position.

4. Burner control apparatus for use with a fuel burner and burnerigniting means under the control of means responsive to the need foroperation of the fuel burner, comprising: a relay having a winding andswitching means which assume a first or a second condition dependingupon whether said winding is deenergized or energized; a safety cutoutdevice having normally closed switch contacts and an electricallyenergizable actuator; a timer having a normally closed switch and anelectrically energizable actuator; combustion responsive means havingfirst and second cold closed switches and a hot closed switch, saidcombustion responsive means arranged to open said first cold closedswitch, close said hot closed switch and then open said second coldclosed switch upon combustion being established; impedance means; aninitial energizing circuit for said relay arranged when completed tooperatively energize said relay winding and in cluding terminals adaptedto be connected to means responsive to the need for operation of thefuel burner, the normally closed switch contacts and actuator of saidsafety cutout device, and said first cold closed switch of saidcombustion responsive means; a first holding circuit for said relay inparallel with the actuator of said safety cutout device including saidimpedance means and said second cold closed switch of said combustionresponsive means, the relative impedance of said initial energizingcircuit and said first holding circuit being such that the actuator ofsaid safety cutout device is operatively energized; a second holdingcircuit for said relay in parallel with the actuator of said safetycutout device including the actuator of said timer and said hot closedswitch of said combustion responsive means; said combustion responsivemeans upon combustion being established opening said initial energizingcircuit for said relay to deenergize the actuator of said cutout deviceand closing said second holding circuit for said relay to energize theactuator of said timer; and circuit means arranged to supply power toterminals adapted to be connected to a fuel burner and burner igniter,said last named circuit means 12 depending upon said relay switchingmeans being in said second condition to supply power to the fuel burnerand upon said timer switch being closed to supply power to the burnerigniter.

5. Burner control apparatus for use with a fuel burner and burnerigniting means under the control of means responsive to the need foroperation of the fuel burner, comprising: a relay having a winding andswitching means which assume a first or a second condition dependingupon whether said winding is operatively deenergized or energized; asafety cutout device having normally closed switch contacts and anelectrically energizable actuator; a timer having a normally closedswitch and an electrically energizable actuator; combustion responsivemeans having first and second cold closed switches and a hot closedswitch, said combustion responsive means arranged to open said firstcold closed switch, close said hot closed switch and then open saidsecond cold closed switch upon combustion being established; impedancemeans; an initial energizing circuit for said relay arranged whencompleted to operatively energize said relay winding and includingterminals adapted to be connected to means responsive to the need foroperation of the fuel burner, the normally closed switch contacts andactuator of said safety cutout device, and said first cold closed switchof said combustion responsive means; a first holding circuit for saidrelay in parallel with the actuator of said safety cutout deviceincluding said impedance means and said second cold closed switch ofsaid combustion responsive means, the relative impedance of said initialenergizing circuit and said first holding circuit being such that theactuator of said safety cutout device is operatively energized; a secondholding circuit for said relay in parallel with the actuator of saidsafety cutout device including the actuator of said timer and said hotclosed switch of said combustion responsive means; said combustionresponsive means upon combustion being established opening said initialenergizing circuit for said relay to deenergize the actuator of saidcutout device and closing said second holding circuit for said relay toenergize the actuator of said timer; circuit means arranged to supplypower to terminals adapted to be connected to a fuel burner and burnerigniter, said last named circuit means depending upon said relayswitching means being in said second condition to supply power to thefuel burner and upon said timer switch being closed to supply power tothe burner igniter; power input terminals arranged to be connected to asource of power for supplying power to the burner control apparatus; aninitial energizing circuit for the burner control apparatus includingsaid power input terminals, said relay switching means in said firstposition, and said timer switch in closed condition; and a holdingcircuit for the burner control apparatus including said power inputterminals and said relay switching means in said second position.

6. A burner control apparatus for use with a fuel burner having burnerigniting means and means responsive to the need for operation of thefuel burner, comprising; a transformer, a burner control relay havingswitch contacts, a safety cutout device including switch contacts and anelectrically energizable actuator, a timer including a switch and anelectrically energizable actuator, combustion responsive switch meanshaving a first and a second condition of operation depending upon theabsence or presence of flame; an initial energizing circuit for theprimary of said transformer including said timer switch, a holdingenergizing circuit for the primary of said transformer including saidrelay switch contacts; an initial energizing circuit for said relayincluding the secondary of said transformer, the actuator of said safetycutout device, said combustion responsive switch means in said firstcondition of operation, and terminals adapted to be connected to meansresponsive to the need for operation of the fuel burner; a holdingenergizing circuit for said relay including the actuator of said timerand said combustion responsive switch means in said second condition ofoperation; said combustion responsive switch means being effective uponthe establishment of combustion at the fuel burner to switch from saidinitial energizing circuit for said relay to said holding energizingcircuit for said relay to thereby deenergize the actuator of said safetycutout device and to energize the actuator of said timer; circuit meansincluding said relay switch contacts to supply power to terminalsadapted to be connected to a fuel burner, and circuit means includingsaid relay switch and said timer switch contacts to supply power toterminals adapted to be connected to a burner igniting means.

7. A burner control for use with a fuel burner and burner igniting meansunder the control of means responsive to the need for operation of thefuel burner, comprising: a transformer having a primary and a secondary;an ignition timer having an electrically energizable actuator andarranged after a time delay to actuate first switching means from acircuit closing to a circuit opening condition, second switching meansincluding an actuator and a plurality of switches, said actuator uponenergization thereof being arranged to actuate the switches of saidsecond switching means from a first to a second condition withnegligible time delay, one of said plurality of switches being closedwhen in said first condition and open when in said second condition, theother of said plurality of switches being open when in said firstcondition and closed when in said second condition, circuit meansincluding a switch of said second switching means which is closed insaid second condition adapted to supply power to terminal means arrangedto be connected to a fuel burner, circuit means including said firstswitching means in said circuit closing condition and a switch of saidsecond switching means which is closed in said second condition adaptedto supply power to terminal means arranged to be connected to burnerigniting means; circuit means connecting said timer actuator and saidsecond switch means actuator to the secondary of said transformer to beenergized thereby including terminals arranged to be connected to meansresponsive to the need for operation of the fuel burner; power inputterminals adapted to be connected to a source of power, an initialenergizing circuit for the primary of said transformer including saidlast named terminals, said first switch means in said circuit closingcondition and said one switch of said second switch means which isclosed in said first condition, and a holding circuit for the primary ofsaid transformer to be effective after said first switching means isactuated to circuit opening condition to thereby open said initialenergizing circuit, said holding circuit including said power inputterminals and a switch of said second switch means which is closed insaid second condition.

8. A burner control for use with a fuel burner and an ignition means,comprising: a transformer having a primary and a secondary, a.relayhaving switch means arranged when said relay is energized to complete acircuit supplying power to terminals adapted to be connected to a fuelburner and ignition means, a timer having an electrically energizablerelatively high impedance actuator and a normally closed switch arrangedwhen opened by a predetermined time period of energization of said highimpedance actuator to discontinue the supplying of power to the ignitionmeans terminal, a safety cutout device having an electricallyenergizable low impedance actuator and a normally closed switchconnected in controlling relation to said relay and arranged to beopened after predetermined time period of energization of said lowimpedance actuator, combustion responsive means responsive to combustionat the fuel burner and having a cold closed switch and a hot closedswitch, an initial energizing circuit connecting said relay to thesecondary of said transformer and including said low impedance safetycutout actuator and the cold closed switch of said combustion responsivemeans, a holding circuit for said relay shunting said safety cutoutactuator and said cold closed switch including said high impedance timeractuator and arranged to be completed by the hot closed switch of saidcombustion responsive means, said combustion responsive means therebybeing effective upon response to combustion at the fuel burner todeenergize said safety cutout actuator and energize said timer actuator,an initial energizing circuit for the primary of said transformerincluding said normally closed switch of said timer, and a holdingenergizing circuit for the primary of said transformer including furtherswitch means arranged when said relay is energized to complete saidholding circuit.

9. A burner control apparatus for use with a fuel burner under thecontrol of means responsive of the need for operation of the fuelburner, comprising: a transformer having a primary and a secondary, arelay having in and out contacts; a safety cutout device having normallyclosed contacts and an electrically energizable actuator; a timer havinga normally closed switch and an electrically energizable actuator; meansresponsive to combustion at the fuel burner, combustion responsiveswitch means controlled by said last named means and having a first andsecond operative condition depending upon the absence or presence ofcombustion; an initial energizing circuit connecting said relay to thesecondary of said transformer including said normally closed safetycutout contacts, said safety cutout actuator, said combustion responsiveswitch means in said first condition, and terminals adapted to beconnected to means responsive to the need for operation of thefuelburner; a holding energizing circuit maintaining said relayconnected to the secondary of said transformer including theelectrically energizable actuator of said timer and controlled by saidcombustion responsive switch means in said second condition, saidcombustion responsive switch means arranged to switch from said relayinitial energizing circuit to said holding circuit upon response tocombustion to thereby operatively deenergize said safety cutout actuatorand operatively energize said timer actuator; power input terminals; aninitial power energizing circuit connected to supply power to theprimary of said transformer including said power terminals, said outcontacts of said relay, and said normally closed timer switch; and apower holding circuit to continue the supply of power to the primary ofsaid transformer including the in contacts of said relay.

10. A burner control for use with a fuel burner unit having a fuelsupply component and an ignition component, both of which are energizedduring starting and only the fuel supply component of which is energizedduring running, the fuel burner unit being under the control of meansresponsive to the need for operation of the fuel burner, comprising: aburner control relay having an actuating winding and in and out relayswitch contact means, a bimetal timer having an electrically energizableheater therefor and a closed cold timer switch, an energizing circuitfor said relay including said relay winding and terminals adapted to beconnected to means responsive to the need for operation of the fuelburner, first circuit means arranged for completion by said in relayswitch contact means to supply power to terminal means adapted to beconnected to a fuel burner unit to energize the fuel supply component,second circuit means arranged for completion by said in relay switchcontact means and including said closed cold timer switch to supplypower to terminal means adapted to be connected to the ignitioncomponent, said timer switch being connected in said second circuitmeans to open said second circuit means to deenergize the ignitioncomponent of the fuel burner unit a predetermined time afterenergization of said timer heater, combustion responsive means normallyresponsive to combustion at the burner unit, an energizing circuit forsaid timer heater operatively energizing said heater upon saidcombustion responsive means responding to combustion, an initial powerenergizing circuit controlling the supply of power to the. abovementioned circuits including power input terminals adapted to beconnected to a source of power, said out relay switch contact means andsaid closed cold switch of said timer, and a holding power energizingcircuit for supplying power to the above mentioned circuits includingsaid in relay switch contact means.

11. A burner control apparatus for a fuel burner and burner ignitionmeans under the control of means responsive to the need for operation ofthe fuel burner, comprising: a relay having an electrically energizableactuator and switch means having an energized and deenergized condition;timer means having an electrically energizable actuator and switchmeans, said timer switch means being actuated from a first to a secondcondition with time delay upon energization of said timer actuator;safety cutout means having an electrically energizable actuator andswitch means controlled thereby; combustion responsive means havingmeans responsive to combustion at the fuel burner and having switchmeans controlled thereby, said combustion responsive switch meansassuring a first or a second condition depending upon the absence orpresence of combustion; a transformer having a primary and a secondarywinding; an initial energizing circuit for said primary windingcontrolled by said relay switch means in said deenergized condition andsaid timer switch means in said first condition; a holding energizingcircuit for said primary Winding controlled by said relay switch meansin said energized condition; an energizing circuit for said relayactuator controlled by said safety cutout switch means, said combustionresponsive switch means in said first condition, and by terminalsadapted to be connected to means responsive to the need for operation ofthe fuel burner; a holding energizing circuit for said relay actuatorincluding said timer actuator and controlled by said combustionresponsive switch means in said second condition, said combustionresponsive switch means thereby operatively deenergizing said safetycutout actuator and operatively energizing said timer actuator upon thepresence of combustion; first circuit means controlled by said relayswitch means in said energized condition to supply power to terminalmeans adapted to be connected to the fuel burner, and second circuitmeans controlled by said relay switch means in said energized conditionto supply power under the control of said timer switch means to terminalmeans adapted to be connected to the burner ignition means.

References Cited in the file of this patent UNITED STATES PATENTS2,086,823 Shaw July 13, 1937 2,188,565 Bower Jan. 30, 1940 2,217,886Baak Oct. 15, 1940 2,308,295 Miller Jan. 12, 1943 2,385,426 Taylor etal. Sept. 25, 1945 2,440,700 Rosche May 4, 1948 2,486,612 Pratt Nov. 1,1949 2,552,973 Judson May 15, 1951 2,604,148 Witherspoon July 22, 1952

